Rear brake overheating problem

[Darsmith]

Changed the rear disc brake pads and rotors last week and put in new parking brake shoes. I was careful about adjusting the parking brake so there was little to no rubbing. I drove around (short trips) for a week and checked the brakes periodically. I did not feel any excess warmth around the rims or brake disc area. Last weekend I had the tires off to add springs and shocks. Went for a long drive on Sunday. Did some offroad trails and including some mud and water (nothing over the axles). Drove about 60 mile home and when I turned into the neighborhood I heard the rear brakes squeeling on and off. Pulled into the driveway and checked the brakes. Rear passenger wheel was very hot and the brake disc/drum was too hot to touch. Let it cool down and pulled the tire. The disc came off the axle easily but the drum area had gotten so hot it discolored. The inner drum is very worn but only in one area like the drum is not concentric with the axle. Lots of rubbing in just one area. I put it on the lathe and ran a dial indicator on the drum surface. I only see about .005" of runout compared to the center hole of the disc, so the drum is pretty concentric to the center hole. I then measured the axle center hub and the disc hole and the hole is about .040" larger than the axle center hub (thinking that any slop would allow the disc to run off center. I don't know what to think. Should I pull the axle and measure to see if the end is perpendicular to the axle. Thoughts? Bent axle?

 

[Irun]

Is there excessive wear on the pads or parking brake shoes? If you changed the parking brake shoes, the parking brake mechanisms can be difficult to put back together correctly. If they aren't, they won't self center. I found this out the hard way!

 

[Darsmith]

I'm pretty sure I got it put back together correctly and I didn't have any problems until this weekend. Is it possible that the disc did not get seated properly when I took the tires off for the springs/shocks and put them back on again. I torqued the lug nuts so I had even pressure on all the wheel studs. The wear is only on one section of the disc/drum so if I got the shoes on incorrectly it seems it would wear the entire drum surface. I'll put a dial indicator on the disc to see if it it somehow warped or something.

 

[Goatman]

Any chance the E-brake cable could bind a bit and keep enough tension to cause the shoe to rub? Maybe not every time you release the parking brake, but at least that one time? Try backing the adjuster loose and go for another spin without pulling the E-brake and see if that prevents the problem. If it does re-adjust back and try pull/release the E-brake handle repeatedly (having a buddy will help) and see if it hangs up again.

 

[Darsmith]

I'll give that a try. Thanks.

 

[pagrey]

Jack up the rear and spin the tires. Seems like a bent axle would do that.

 

[Darsmith]

I'm working out of town and will not be able to get back to this project for a while. Thank you for your help. I'll let you all know what/if I find out what's going on with this. Drum is worn only in one area and only one brake shoe is worn on one spot near the brake 'cam', not the adjustment end of the shoe.

 

[chad]

Jack up the rear and spin the tires. Seems like a bent axle would do that.

X2 mine did the exact same thing. I put it on jack stands and ran it. It was easy to see but I couldn’t feel it just driving around.

 

[Darsmith]

Ouch. Guess I'll find out when I get back home and working on it again.

 

[Darsmith]

OK, got around to working on the brakes again. I pulled the right rear axle and put it on the lathe. I have less than .005" runout in the center of the axle shaft. I put a dial indicator on the axle end plate. I had about .001" of runout and about .0015" runout in the plate face. I pressed out the studs and trued up the end plate face to less than .0005" to the shaft. I did this because the end plate also had some sort of baked on debris that would have made the disc not sit true to the plate. Pressed in new studs and put it all back together. I put the disc back on and torqued it without the wheel. Dial indicator shows about .001" runout in both the disc face and about the same with regard to the disc being concentric with the axle while turning. I did check the e-brake setup and the shoe that was rubbing sat slightly higher than the other pad. It had a high spot in the shoe plate where it contacts the e-brake cam. I must have missed that when I installed them. Made a few passes with a file and got it to match with the other shoe. Adjusted up the e-brakes and ran it for about 20 mile. No overheating problem. Interesting problem... still not quite sure everything I did will guarantee it won't reappear some time down the road. I never did find a definite issue that would have caused what I experienced.

 

[chad]

Thanks for the follow up. It’s always interesting how problems get solved.